Lithium-ion and lithium-polymer battery packs are used as a rechargeable energy source for many electronics applications, particularly consumer electronic device such as cellular mobile telephones. Lithium-based battery packs often require a switch device to protect the lithium cell or cells from overcharge. Current switch devices have limited capability for reliability under severe fault conditions that might occur as a result of a failed battery charger. If not mitigated, catastrophic failure of the lithium cells is possible.
What is needed is a circuit arrangement that provides supplemental protection for a switch device in an overcharge protection device, such as those used in rechargeable battery packs.